title: Ionized o-, m-, and p-difluorobenzene dissociate through ring-opened intermediates: a TPEPICO investigation.
abstract: Threshold photoelectron photoion coincidence (TPEPICO) experiments have shown that o-, m-, and p-difluorobenzene ions dissociate via a common, ring-opened intermediate and not via ionized p-difluorobenzene. Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental breakdown curves yields activation energies for the initial isomerization of 4.48 +/- 0.05, 4.55 +/- 0.05, and 4.68 +/- 0.05 eV for o-, m-, and p-difluorobenzene, respectively. These values place each ion at a similar absolute energy and thus similar transition states. A large positive DeltaS(double dagger) for each ion (ca 100 J K(-1) mol(-1)) suggests a ring-opened structure for these transition states.
authors.affiliation: Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Boulanger
authors.forename: David M P
authors.initials: DM
authors.lastname: Holland
authors.forename: David A
authors.initials: DA
authors.lastname: Shaw
authors.forename: Paul M
authors.initials: PM
authors.lastname: Mayer